The present invention is well adapted to use Internet communications. As is well known, the Internet is a network of computer networks having no single owner or controller and including large and small, public and private networks, and in which any connected computer running Internet Protocol software is, subject to security controls, capable of exchanging information with any other computer which is also connected to the Internet. This composite collection of networks which have agreed to connect to one another relies on no single transmission medium (for example, bidirectional communication can occur via satellite links, fiberoptic trunk lines, telephone lines, cable TV wires and local radio links).
The World Wide Web Internet service (‘Web’ hereafter) is a wide area information retrieval facility which provides access to an enormous quantity of network-accessible information. Information about the World Wide Web can be found in “Spinning the Web” by Andrew Ford (International Thomson Publishing, London 1995) and “The World Wide Web Unleashed” by John December and Neil Randall (SAMS Publishing, Indianapolis 1994). Use of the Web is growing at an explosive rate because of its combination of flexibility, portability and ease-of-use, coupled with interactive multimedia presentation capabilities. The Web allows any computer connected to the Internet and having the appropriate software and hardware configuration to retrieve any document that has been made publicly available anywhere on the Internet. The retrievable documents on the Web include ‘HyperMedia’ documents—i.e. documents which may be text documents or other forms of media such as sounds and images and which may have links (‘hyperlinks’—see below) to other documents. The format of such documents on the Web is a standard format in HTML (HyperText Markup Language), such that a document created on one operating system and hardware platform can be read by a user on any other platform that has an appropriate Web Browser (see below). HTML is associated with a specific communication protocol known as HyperText Transfer Protocol (http). Images may be stored in separate graphics files, for example in standard GIF or JPEG format, which are referenced in the HTML text for retrieval with the HTML text.
Users access this information using a ‘Web Browser’, which is software installed on the user's computer having facilities for connecting to a Web server via the Internet and for retrieving documents from the Web server and presenting them. A Web server in this context is a computer program which provides services (serving requested HTML pages or files) in response to requests from other ‘client’ computer programs; a Web server computer is a computer running a Web server program. Currently available Web Browsers include Netscape Navigator from Netscape Communications Corporation and Internet Explorer from Microsoft Corporation. Such Browsers understand HTML and other Web standard formats and can display or output files correctly in these formats. The Web is structured as pages or files which each have a particular Universal Resource Locator (or URL). The URL is an address reference which denotes, amongst other things, both the server machine and the particular file or page on that machine. A user can type in particular URLs or jump from one page to an associated page by means of ‘hyperlinks’—that is, a word or symbol on a page can be associated with a URL for another page which is selectable to cause the Browser to send a request which retrieves, and then to display, the relevant page. The preferred user interface for such Browser selection is the graphical ‘point-and-click’ interface (i.e. links are selected by moving a cursor to a particular word or symbol on a display and then pressing a mouse button). The words, images and symbols having associated hyperlinks are identifiable by a user as “hot spots” (for example, the relevant text may be highlighted or underlined, or the cursor may change its appearance as it passes over the hot spots). There may be many pages resident on a single server, and associated hyperlinked pages may be located on different servers.
Web pages are thus well known to be identifiable through URLs, such as http://www.pc.ibm.com/data.htm. This example illustrates three components of the URL: “http” identifies the protocol to be used by a Web browser for access to the page; “www.pc.ibm.com” identifies the target computer (this computer name is converted to its numeric-form Internet address); and “data.htm” identifies the page to be accessed on that computer. More complex examples having additional parameters are also possible, such that specific data may be passed from the client computer to the server computer in a URL specification.
For security reasons, Web Servers typically require a so-called “firewall” to prevent unauthorised access. A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from non-authorised users. An enterprise with an intranet (a private network using Internet protocols) that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to. An intranet can include an “extranet” which is the part of an intranet which is made accessible to authorised business partners.
A firewall, working closely with a router program, filters all network packets to determine whether to forward them toward their destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. There are a number of known firewall screening methods, such as to screen requests to make sure they come from acceptable (previously identified) domain names and IP addresses. For mobile users, firewalls allow remote access to the private network by the use of secure logon procedures and authentication certificates.
With the increasing provision of electronic information and control units within vehicles, and also in the home, there is a requirement for a mechanism enabling remote computers to be able to access these electronic information and control units. For example, a car rental firm may wish to check the location of or status information relating to each of their cars from a computer at head office, and a car user may wish to set car climate controls from his home computer. Furthermore, there is a requirement for such a mechanism with sufficient security provision to prevent unauthorised access to control units in vehicles or in the home. However, the above-described resource access mechanism of a Web Browser connecting to a Web Server, and the Web Server implementing a firewall, cannot easily be implemented by installing a Web server in a car or in the home. This is because Web Servers require an administrator for ongoing maintenance as well as for initial set-up, and a firewall additionally requires continuous update and maintenance to watch its protocol files for unauthorised access attempts. Implementing a Web Server within a car would have unmanageable security problems. Similar problems exist in any wide area network.